Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

Chiral carbon quantum dots (CQDs) with chirality, fluorescence and biocompatibility were synthesized by a one-step method with L-/D-tryptophan (L-/D-Trp), as both carbon source and chiral source. Levogyration-/dextrorotation-CQDs (L-/D-CQDs) were characterized by transmission electron microscopy, Fourier transform infrared spectrometry, ultraviolet-visible absorption, excitation and emission spectrometry and circular dichroism (CD) spectrometry. Results show that L-CQDs and D-CQDs present similar spherical morphology, functional groups and optical properties. The CD signal, around 220, 240 and 290 nm are opposite and symmetric, which conclusively demonstrates that L-CQDs and D-CQDs are enantiomers. Besides the CD signal around 220 nm from the inheritance of L-/ DTrp, two new chiral signals around 240 and 290 nm were induced by chiral environment.